The present invention relates to an elastic swivel, of the type having at least a spring connection member comprising:
a central core external having an attachment surface of truncated conical form; PA1 an outer collar disposed coaxially about the central core and internally provided with an attachment surface of truncated conical form the vertex of which is oriented in the same direction as the vertex of the attachment surface of the core; PA1 at least one elastic ring made of elastomeric material, having the form of a truncated cone and being rigidly engaged between the outer frusto-conical surface of the core and the inner frusto-conical surface of the collar. PA1 axial oscillations; PA1 radial oscillations; PA1 rotational oscillations about the geometric axis of the joint; PA1 huntings about an axis perpendicular to the geometric axis of the joint.
The elastic swivel in question can be widely used in many fields of the mechanical industry, such as for example in the manufacture of suspensions for road and railway vehicles and/or in any situation in which the necessity arises of connecting two members or parts of a machinery susceptible of mutual oscillations in different directions.
In particular, in the course of the present description reference will be made, by way of example only, to the application of the elastic swivel to suspensions for bogies in the railway field.
It is known that when it is necessary to connect two members of a machine or apparatus giving them the possibility of mutual oscillation elastic swivels are often used which essentially consist of one or more spring connection members, each of which comprises a central core externally having an attachment surface of truncated conical form, an outer collar provided with an inner attachment surface of truncated conical form the tapering of which is equal to that of the attachment surface in the core, as well as a ring made of elastomeric material, of truncated conical form too, connected to the attachment surfaces of the core and collar by a rubber-metal junction process.
The parts that, must be mutually connected by the above describe swivel and are engaged to the central core and outer collar respectively, will be able to elastically oscillate according to different directions.
In more detail, the possible elastic oscillations in the different directions are classified according to four different types:
By choosing each time different construction solutions it is possible to impart more or less elasticity to the joint depending upon requirements, in connection with one or more of the above listed oscillation types.
For example, in making a swivel it is common to couple two connection members which are disposed coaxially and in mirror image relationship in order to balance the elastic behavior thereof in the two ways of the axial oscillation direction.
It is also known from the Italian Patent No. 1,006,248 to manufacture an elastic joint in such a manner that, after the assembling, the elastic ring or rings provided therein are precompressed between the central core and the outer collar.
This construction solution is normally adopted in order to reduce the ratio value between the radial stiffness and axial stiffness in the joint.
The behavior of the joint in the different oscillation directions can also be established, within some parameters, by the choice of suitable shapes and sizes of the elastic ring or rings interposed between the core and the outer collar.
It is however to be pointed out that at the present state of the art serious difficulties are encountered in the manufacture of elastic swivels offering a satisfactory behavior and in particular a high fatigue limit in connection with huntings.
In fact it has been found that when an elastic swivel is particularly stressed by this type of oscillation, it undergoes fatigue yieldings that usually result in the separation of the rubber ring from the core and/or outer collar at the edges defining the major base of the frusto-conical configuration of the ring itself.